1. Technical Field
This invention relates generally to corrective lenses, and more particularly to a new and improved lens system having selectable optical characteristics.
2. Background Information
We sometimes use multi-segmented optical surfaces to correct or compensate for different vision disorders, tailoring the optical characteristic of each segment to a specific patient need. Thus, one lens can be used to compensate for more than just one disorder. Bifocal and trifocal spectacle lenses as well as multi-segmented contact lenses, corneal implant lenses, and intraocular lenses share this attribute and function.
The patient selects the optical characteristics desired. In order to select the desired optical characteristics of a bifocal lens, for example, the patient merely looks through the appropriate segment. But selecting the desired optical characteristics with other lenses is more complicated.
Consider, for example, a teledioptric lens system utilized to compensate for macular degeneration. Recall that macular degeneration affects the central retinal area known as the macula and it can lead to a gradual or sudden loss of vision to the level of 20/200 or less. It may affect only about one-quarter to four square millimeters of the central retinal area, thereby leaving 95%-99% of the retina unaffected Thus, near vision, for example, for reading and watching television can be lost while far vision remains intact.
Telescopic systems that increase the retinal image size of a given object have been used to compensate for such loss of near vision. Such a system is described in pending U.S patent application Ser. No. 141,482 and it may include an intraocular lens (IOL) or optical implant which replaces the natural lens, the implant having both a diverging central portion and a converging peripheral portion. The diverging portion operates in conjunction with spectacles configured as an ocular telescope that focuses images for near vision while the converging portion operates in the absence of the spectacles to provide far vision.
With such a system, the patient selects the desired optical characteristics by donning or removing the spectacles. In other words, the patient selects the diverging portion of the intraocular lens by using the spectacles and the converging portion by removing them. But utilizing the spectacles in this way to select the diverging portion only emphasizes the diverging portion instead of stopping light from passing through the converging portion, and this can impair the patient's vision. Similar problems may accompany use of multi-segmented contact and corneal implant lenses.
Thus, it is desirable to have some way of selecting only the desired segment or portion without also having light pass through the other segment or portion